1, 2-dimethylcyclobutenedione and method of preparation



3,109,147 Patented Feb. 9, 1965 3,169,147 1,2-DIMETHYLCYCLOBUTENEDIONEAND METHOD @F PREPARATION Alfred T. Blomquist and Richard A. Vierling,both of llthaca, N.Y., assignors to The B. F. Goodrich Company, NewYork, N.Y., a corporation of New York No Drawing. Filed Got. 24, 1961,Ser. No. 147,178 4 Claims. (Cl. 260-586) This invention relates to a newand useful cyclic diketone and to a method for its preparation and moreparticularly refers to 1,Z-dimethylcyclobutenedione and to the method ofits preparation by hydrolysis of 1,2- dimethyltetrafiuorocyclobutenewith strong sulfuric acid or polyphosphoric acid at a temperature offrom about 50 C. to about the reflux temperature of the mixture.

The compound of this invention has the structure It i: useful as achemical reagent for characterizing hydrazines and can be employed as araw material for preparing dimethylmaleic anhydride.

The 1,2-dimethyltetrafluorocyclobutene, which is bydrolyzed to1,2-dimethylcyclobutenedione can-be prepared by methylating perfluorocyclobutene with methyl lithium by a modification of the proceduredescribed by S. Dixon,

J. Org. Chem. 21, 400 (1956).

To a dry, nitrogen swept 5-liter, 3-necked flask fitted with a stirrerand two Dry 'Ice condensers, were added 3000 ml. of dry diethyl etherand 65 g. of lithium wire which had been cut into pieces of about /2inch length. The mixture was cooled to about 0 C. in a Dry Iceacetonebath and then methyl bromide was condensed into the stirred mixtureuntil the lithium completely disappeared. The bath was subsequentlycooled to -45 C. and 324 g. of perfluorocyclobutene were slowlydistilled into the stirred mixture over a two to three hour period. Themixture was then stirred for an additional two hours at 45 C. and thenallowed to warm slowly for three hours before removing from the bath.

Excess methyl lithium was decomposed with 200 ml. of a 1:1 aqueous HClsolution. The ether solution was decanted from the heavy whiteprecipitate which formed. The ethereal solution was washed with 100 ml.of water, several 100ml. portions of saturated sodium carbonate solutionand a final 100-ml. portion of water." The other solution was then driedover magnesium sulfate, filtered and the ether was distilled. The crudeorn-o-or,

. on,- or

was collected asa distillate, B.P. 95-104 C. This was vigorously stirredwith 200 ml. of water to remove the last traces of HF. The organic layerwas again dried over magnesium sulfate and then fractionally distilledat 100-104 C. The final product had an 11 of 1.3478.

When the methylation was carried out at temperatures below --45 C. thereaction was sluggish, as evidenced by the large amount of unreactedperfluorocyclobutene. If the reaction was carried out at -40 C. it wastoo vigorous to be controlled and resulted in a considerable amount oftar formation.

The examples which follow are intended to illustrate the invention, notto limit its scope. In all instances parts are given by weight unlessotherwise specified.

Example I A mixture of 20 g. of1,2-dimethyl-3,3,4,4-tetraflu0rocyclobutene and 100 ml. of 96% sulfuricacid was stirred vigorously and heated to 6570 C. for one hour in adried over magnesium sulfate and concentrated in vacuo to yield a darkred oil. Fractional distillation of the oil yielded 6.29 g. of a yellowgreen liquid, which on further purification had a 13.1. of 76 C. at 2mm.- and an 11 of 1.4893.

On analysis the following results were obtained.

Found: C, 65.41; H, 5.49; mol. Wt., 127 (Rast). Ca1- culated for G l-I 0C, 65.44; H, 5.49; mol. wt., 110.

The 1,Z-dimethylcyclobutenedione solidified at about 25 C., so thatcondensation temperature must be controlled to avoid solidification inthe condenser.

The pure diketone is quite stable. It can be stored at room temperaturefor several weeks without any notitceable change in the absence ofdirection sunlight. It is soluble in water, ether, chloroform, benzene,dioxane, acetonitrile and mineral acids.

The'compound of this invention showed infrared absorption bands at 5.60and 5.67 microns (unresolved doublet) with a shoulder at 5.49 microns,weak absorp: tion at 2.83 microns, and strongsharp absorption at 6.21microns.

The n.m.r. proton spectrum shows only one unresolved peak at 2.40 p.p.m.to lower field than the resonance of protons in an internal tetramethylsilane standard.

The n.m.r. spectrum of biacetyl showed a single unresolved peak in thesame region.

In ethanol solution the ultraviolet absorption of CH -OO==O CH C=0 hadthe following maxima (epsilons in parentheses) 216 (18,800), 340 (26)with a shoulder at 355 (23) millimicrons. V

When the ethanol stock solution of the compound stood for 9 days theintensity at the maximum 216 millimicrons decreased to 13,500 and after16 days to 12,080 epsilons. This indicates a slow deterioration of thediketone.

Example 11 Polyphosphoric acid was prepared by adding 140 g. of P 0 in20-g. portions to ml. of 85% orthophosphoric acid, followed by heatingon a steam bath for three to four hours.

To a 500-ml. flask equipped with a stirrer, condenser and thermometer,were added 300 grams of polyphosphoric acid and preheated to -10S C.Then 20 g. of 1 butenedione were the same as those obtained in Example1.

Substitution of 100% H PO made by dissolving 95 g. of P in 248 g. of 85%orthophosphoric acid, for the polyphosphoric acid and then running thereaction under substantially the same conditions as described in Example2 results in the production of only about 15% of a very impure diketonewhich tends to decompose within a very few hours after distillation, asevidenced by the development of a deep green color.

When sulfuric acid is employed as the hydrolytic agent it should containfrom 90 to 98% H 80 but it is preferred to use 96 to 97% acid. Thepolyphosphoric acid should analyze about 77% or more i O and can be ashigh as 95% P 0 Ordinary technical grade, concentrated sulfuric acid isusually satisfactory. For best results the quantity of either sulfuricor polyphosphoric acid employed in the reaction should be sufficient todissolve the dimethylperfluorocyclobutene fairly rapidly at the reactiontemperature. This will require about 4 ml. of either sulfuric orpolyphosphoric acid per gram of the dimethylperfluorocyclobutene. Thereaction proceeds most rapidly and smoothly when theperfiuorocyclobutene is dissolved in the hydrolyzing medium, andundesirable by-products are reduced to a minimum. However, smalleramounts of hydrolyzing medium can be used at a sacrifice of yield of thedesired diketone. There is no maximum amount of hydrolyzing medium thatcan be used. The sole limiting factor is the practicality of the work-upprocedures employed when large quantities of acid are used.

The temperature at which the reaction can be run varies somewhatdepending on the strength of acid used. With sulfuric acid of 90-92%strength the temperature can'be as low as about 50 C. and as high asabout 100 C. with an increase in concentration of the sulfuric acid upto 98%, the maximum temperature should not exceed about 8085 C. to avoidundue amounts of by-products.

The most desirable reaction temperatures for obtaining best yields ofthe diketone are also dependent on the P 0 content of the polyphosphoricacid. Thus, if the P 0 content of the polyphosphoric acid is about 90%,the lower range of temperature is best (SO-75 C.), but with a P 0content in the 77 to 80% range the temperature can go as high as thereflux temperature, which may vary between about 105 to about 120 C.

The reaction, of course, can be carried out under induced pressure or atsub-atmospheric pressure.

The compound of this invention is useful for preparing dimethylmaleicanhydride, which can be employed for making polyesters or forcopolymerizing with other monoor diunsaturated monomers by additionpolymerizations, using procedures known in the art. It is also usefulfor characterizing hydrazines, because through controlled conditionseither the monoor dihydrazones can be prepared.

To a solution of 1.61 'g. of

CH;-C--C=O orn- =0 in 15 ml. water were added 25 g. of a 30-35% hydrogenperoxide solution. Within 5 minutes a mild exothermic reaction occurred,and dimethylmaleic anhydride began to crystallize. After 1.5 hours themixture was filtered and the white solid was washed with water. A 71%yield of dimethylrnaleic anhydride having an MP. of 93- 94 C. aftersublimation at 35 C. and 0.15 mm. was obtained. A mixed melting pointwith authentic dimethylmaleic anhydride was 93.595 C.

A mono-2,4-dinitrophenylhydrazone derivative was prepared by thedropwise addition of one equivalent of 2,4- dinitrophenylhydrazine overa 25-hour period to an ethanol solution of one equivalent of Thederivative was obtained in the form of hard, redorange plates. It had amelting point of 205-208 C. (with decomposition) after severalrecrystallizations from ethyl acetate.

Analysis.-Calculated: C, 49.65; H, 3.47; N, 19.30. Found: C, 49.68; H,3.49; N, 19.45.

A ditosylhydrazone was prepared by evaporating a methanol solutioncontaining equimolar quantities of the diketone andP-toluenesulfonylhydrazine on a hot plate until crystals first appeared.On cooling the ture, the derivative was obtained in the form of whiteneedle-like crystals. After several recrystallizations from 95% ethanolthe crystals had a melting point of 190- 191 C. with decomposition.

Analysis.-Calculated: C, 53.70; H, 4.97; N, 12.55. Found: C, 53.71; H,5.02; N, 12.60. a

We claim:

1. A method for preparing 1,Z-dimethylcyclobutenedione comprisingblending CI-I i-GFQ with an excess of polyphosphoric acid having a P 0content from about 77 to about 95 by weight, heating to a temperature ofabout 50 C. to about reflux temperature of the mixture and recovering 2.The method of claim 1 in which the polyphosphoric acid is made by mixing140 g. of P 0 with 90 ml. of H PO and heating to -100 C. for 2 to 3hours.

3. The method of claim 1 in which the reaction temperature is 90-105 C.

cH3-c-( 3=o 015a- -o=o References Cited by the Examiner UNITED STATESPATENTS 2,650,939 9/53 McBee et al. 260-586 OTHER REFERENCES Blomquistet al.: American Chemical Society Abstracts of papers, th Meeting, 1959,pp. 54-0.

LEON ZITVER,'Primary Examiner.

CHARLES E. PARKER, Examiner,

1. A METHOD FOR PREPARING 1,2-DIMETHYLCYCLOBUTENEDIONE COMPRISINGBLENDING